Only did it once. one of my friends was the GM and it was a sort of wild west post apoc setting, it was a mess but it was our first year of RPGs. My character was a gunslinging engineer and while that might sound like Roland it was a decade before I ever read the Dark Tower, and it was inspired by the Sorcerer's Crusade material from white wolf. My character had designed a multiple barrel 'gun' that was bigger than a pistol, and not quite a rifle. It functioned like a shotgun because the GM ruled that it had to be horribly inaccurate, so I gave it six barrels. It could fire one barrel at a time or pull the trigger on all six for a Hail Mary attack. It ended up being really useful at point blank range, but to get that close, my non-armor wearing PC had to get within claw range. Last time it was used, I stuck it in the face of a juvenile dragon and pretty much blew it's head off. Then my character retired.